Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
from collections import deque
h, w = map(int, input().split())
c = []
for _ in range(h):
    c.append(input())

ans = 0
for i in range(h):
    for j in range(w):
        if c[i][j] == ".": ans+=1

d = [[-1]*w for _ in range(h)]
d[0][0] = 1
que = deque([[0, 0]])
while que:
    x, y = que.popleft()
    for i, j in [[1,0],[0,1],[-1,0],[0,-1]]:
        nx, ny = x+i, y+j
        if 0<=nx<w and 0<=ny<h and c[ny][nx]=="." and d[ny][nx]==-1:
            d[ny][nx] = d[y][x]+1
            que.append([nx, ny])
if d[h-1][w-1] == -1:
    print(-1)
else:
    print(ans-d[h-1][w-1])